Port Ranges
Security Status Legend
How to look up a port
- Type a port number between 0 and 65535, for example
8443, and press Enter or Lookup. - Or type part of a service name, such as
ssh,mysqlorldap. Every IANA service whose name contains the text is listed (first 50 shown); click a row for details. - Pick a Transport (TCP, UDP, SCTP, DCCP) to keep only the services registered on it, and to show that transport's service first when you look up a number.
- Use the Common ports buttons for the usual suspects: FTP, SSH, SMTP, DNS, HTTP(S), MySQL, RDP, PostgreSQL.
The data is the IANA Service Name and Transport Protocol Port Number Registry, about 6,500 port numbers, loaded as a static file and searched in your browser. Nothing you type is sent to a server.
Reading the result
- Service and protocols: the IANA service name and the transports registered for it. Port 443 shows
HTTPSwith TCP and UDP (the UDP entry is what HTTP/3, QUIC, uses); the separate SCTP registration (RFC 9260) is listed under other services. When a number carries different services per transport, each lists its own: 514 isshellon TCP andsyslogon UDP. - Description and Reference: the registry description and, where IANA gives one, the RFC that defines the protocol.
- Security status: set for about 50 commonly exposed ports. Secure means encrypted by design, Conditional means it depends on configuration (SMTP on 25 with or without STARTTLS), Insecure and Deprecated mean plaintext or obsolete. Other ports show Unknown, which is not a verdict.
- Secure alternative and Firewall recommendation: what to use instead (SSH on 22 for Telnet on 23) and how far to expose it.
- Port range: well-known (0-1023) or registered (1024-49151). Dynamic ports (49152-65535) are never assigned by IANA, so they return no entry.
Frequently asked questions
What port does RDP use?
Remote Desktop uses TCP and UDP port 3389. IANA registers it under the service name ms-wbt-server, so a search for "rdp" finds other RDP-related entries but not 3389 itself: search the number instead.
Why does a port number show no service?
Many numbers in the IANA registry are unassigned or reserved, and ports 49152-65535 are never assigned. An open port without an entry is just an application picking a free number; identify it on the host with ss -tlnp (Linux) or netstat -ano (Windows).
Does an IANA assignment tell me what is really running on a port?
No. The registry records which service a number is reserved for, not what listens on a given host. Any program can bind any free port, and attackers often use well-known ports such as 443 to blend in. Confirm with a service scan, for example nmap -sV -p 8443 host, and review the output in the Nmap XML parser.
What is the difference between TCP and UDP ports?
They are separate number spaces: TCP 53 and UDP 53 are different sockets. IANA usually registers a service for both even if it only uses one in practice. The badges in the result show the transports the registry lists for the service shown (TCP, UDP, SCTP, DCCP); other services on the same number list their own. One number can even carry different services per transport: 514 is shell on TCP and syslog on UDP.
Which ports should never be open to the internet?
As a rule: Telnet (23), SMB (445), RDP (3389), database ports such as 1433, 3306 and 5432, and admin interfaces. Look each one up here for the security note and suggested alternative, and put remote access behind a VPN.